The present invention relates to a method for manufacturing a honeycomb structure having plugging portions formed in at least a part of the opening end portions of the cells of the honeycomb structure, and it also relates to a manufacturing apparatus of the structure.
A requirement for removing particulate matter and toxic substances contained in exhaust gas discharged from internal combustion engines, boilers and the like has grown in light of influence on environment. In particular, regulations on removal of particulate matter (hereinafter sometimes referred to as particulate matter (PM)) discharged from diesel engines tend to be strengthen in Europe and the United States as well as Japan, and a honeycomb structure is used in a trapping filter for removing the PM.
Examples of the filter used for such a purpose include a honeycomb filter utilizing a plugged honeycomb structure including a honeycomb structure in which a plurality of cells constituting fluid passages are partitioned and formed by porous partition walls by the partition walls and plugging portions which alternately plug one opening end and the other opening end of each of the cells. According to such a honeycomb filter, an exhaust gas G1 is allowed to flow into cells from the exhaust gas inflow side end face of the filter, whereby particulates contained in the exhaust gas are trapped by the partition walls when the exhaust gas G1 passes through the partition walls. In consequence, a purified gas G2 from which the particulates have been removed can be discharged from the purified gas outflow side end face of the filter.
Moreover, as a method for manufacturing the above-mentioned plugged honeycomb structure, for example, there is proposed a method which includes the steps of attaching an adhesive sheet or the like to one end face of a honeycomb structure (a non-fired dried ceramic body); making holes in only the portions corresponding to the cells to be plugged (plugged cells) in the adhesive sheet or the like by laser processing or the like using image processing to form a mask; immersing, in slurry (ceramic slurry), the end face of the honeycomb structure to which the mask is attached to fill the slurry into the cells to be plugged, thereby forming plugging portions; subjecting the other end face of the honeycomb structure to the same steps; and drying and firing the honeycomb structure to obtain the plugged honeycomb structure (e.g., see Patent Document 1).
[Patent Document 1] JP-A-2001-300922
However, according to the method of making the holes in the adhesive sheet and immersing, in slurry, the honeycomb structure provided with this adhesive sheet as the mask as described above, operation time is required for leveling the slurry in which the structure is to be immersed, and this is a factor for cost increase. Moreover, the leveling is very delicate, and an outer peripheral portion becomes thick or thin owing to slight displacement, so that it is difficult to obtain a uniform plugging depth. A leveling accuracy matches a depth accuracy, so that considerable amounts of labor and time are required for the leveling step. In particular, when a large-sized honeycomb structure is subjected to plugging in the same manner, it is more difficult. Moreover, a film attached to the structure needs to be folded in a large amount so that a side face portion of the immersed honeycomb structure is not made dirty, but it is not easy to appropriately fold the film. In addition, peeling off requires great care.